Organotin mercapto ethylene carboxylates and method for producing same



United States Patent 3,293,273 ORGANOTIN MERCAPTO ETHYLENE CARBOX- YLATES AND METHOD FOR PRODUCING SAME Carl R. Gloskey, Stirling, N.J., assignor to M & T Chemicals Inc., New York, N.Y., a corporation of Delaware N0 Drawing. Filed Apr. 9, 1963, Ser. No. 271,590 Claims. (Cl. 260429.7)

This invention relates to novel organic compounds. More specifically it relates to organotin mercapto compounds and to resin composition stabilized therewith.

Various organotin mercaptide type compounds have been mixed with chlorine-containing resins including polyvinyl chloride type resins to improve the properties of these resins. These compounds have been found to be particulanly effective in increasing the stability of the noted resins against deterioration by heat and light. Although many such compounds have been used as heat and light stabilizers, they are commonly characterized by defects. For example, many of these compounds are highly polymeric in nature and may therefore be insoluble or not readily soluble in commonly used organic solvents such as toluene. Other stabilizers may be characterized by their undesirably high odor which renders them less than fully satisfactory for many uses. Some stabilizers may be either heat or light stabilizers; but there is no presently available stabilizer which is believed to possess outstanding ability to simultaneously stabilize against deterioration from. both heat and light.

It is an object of this invention to provide a novel organotin mercapto stabilize-r compound characterized by its ability to effect stabilization of chlorine-containing resins against deterioration by heat and light. Other objects will be apparent to those skilled in the art on inspection of the following description.

In accordance with certain of its aspects, the novel organotin compound of this invention may be prepared by reaction of substantially equimolar amounts of RR"SnO and /3-mercaptopropioni:c acid HSCH CH COO'H, together with R SnCl +1 in amount of 0.05 to 0.20 mole per mole of HSCH CH COOH wherein R, R, and R" may each be selected from the group consisting of alkyl, alkenyl, alkynyl, cyoloalkyl, aryl, aralkyl, and alkaryl, a is less than 3, and a+b equals 3. The so-prepared product may In practice of this invention, the compound R'RSn0 may be a compound wherein R and R", which may be different but which preferably are the same, may be hydrocarbon i.e. selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, a-ryl, aralkyl, and alkaryl, including such moieties when inertly substituted. When R and R are alkyl, they may typically include methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-lbutyl, tbutyl, n-amyl, iso-amyl, n-hexyl, n-heptyl, n-octyl, ndecyl, etc. When R and R" are alkenyl, they may typically include vinyl, allyl, buten-l-yl, etc. When R and R" are alkynyl, they may typically include ethynyl, propyn-l-yl, n-butyn-l-yl, etc. When R and R are cycloalkyl, they may include cyclohexyl, cycloheptyl, cyolooctyl, methyl cyclohexyl, etc. When R and R" are aryl, they may typically include phenyl, naphthl, etc. When R and R are aralkyl, they may typically include benzyl, w-phenylpropyl, etc. When R and R are alkaryl, they may typically include tolyl, xylyl, etc.

Typical compounds R'RSnO may include dimethyltin oxide, diethyltin oxide, di-n-propyltin oxide, di-n- "ice butyltin oxide, di-isopropyltin oxide, di-isobutyltin oxide, diphenyltin oxide, di-n-benzyltin oxide, di-n-octyltin OX- ide, di-n-hexyltin oxide, dicyolohexyltin oxide, di-allyltin oxide, butyl propyltin oxide, etc.

The preferred compound RR"SnO may be that wherein R and R" are the same. Preferably R and R may be lower alkyl, i.e. alkyl groups having less than about 10 carbon atoms. The preferred compound may be di-nbutyltin oxide.

The ,B-mercaptopropionic acid, HSCH CH COOH (m. wt. which may be employed maybe that commercially available. It may be a clear liquid having a sp. g. of 1.218 (2% 0.), MP. 16.8 C., and RP. 110.5 C.- 111.5 C. at 15 mm. Hg.

According to a preferred embodiment of this invention, the RR"SnO, preferably dibutyltin oxide, and the fl-mercaptopropionic acid may be reacted in equimolar quantities as follows:

The RR"SnO and the fi mencaptopropionic acid may be added to a reaction mixture wherein they may react to form by-product water. Optionally the reaction may be conducted in the presence of an inert solvent, preferably one which may form an azeotrope with the by-product Water. Preferred solvents may include acetone, heptane, and aromatic hydrocarbon solvents including toluene and xylene. Prefer-ably the solvents may be present in amount sufficient to permit removal of the by-product Water by azeotropic distillation. Typically 10-25, say 15 parts of solvent per 100 parts of product or about 2. to 5 parts of solvent per part of lby-product wate-r may be present. The reactants may preferably be heated to reflux temperature typically C.-135 C., say C. during which time by-product Water of reaction may be azeotropica-lly distilled off.

Completion of the reaction, as measured by recovery of one mole of water per mole of R'RSnO (if this compound is present in amount less than that of the acid present), may be observed after 15-45 minutes, say 30 minutes. Remaining solvent may be removed preferably by distillation under vacuum, typically at 10-50 mm. Hg pressure, say 25 mm. Hg over 15-45 minutes, say 30 minutes.

The product so produce-d may be recovered as residue in yield approaching 100%. Although this product, prepared preferably from equimolar amounts of the charge materials, may be thought of as having the indeterminate monomeric Formula I supra, it appears more likely that it has the semi-empirical Formula II supra. In this formula, it appears that x may be an integer typically 3-8, say 5, i.e. that this many of the designated moieties may be linked together. Typically the product so formed may have a molecular weight as determined by melting point depression which indicates that 6-8 of these moieties may be joined together. This material may be found to be of limited solubility in organic solvents such as toluene.

In practice of the instant invention, there may be added to the reaction mixture, prior to the recovery therefrom of said composition, 0.05-0.20 moles of R SnCl per mole of fi-mercaptopropionic acid. In the compound R SnCl R may be selected from the group con sisting of R and R". R may be the same as R or R,

Preferably a may be less than 3, and a-l-b may dichloride.

The compound R SnCl -h may be added to the reaction mixture at the beginning of the reaction, i.e., simultaneously with the R'RSnO and the fl-mercaptopropionic acid, or during the course of the reaction, or preferably after the product, putatively polymeric material may be prepared. Thus, it may not be necessary to isolate the latter material prior to adding R SnCl to the reaction mixture. Reaction of R SnCl with the polymeric material or with the compounds from which it may be prepared may be as follows:

Equation 3 schematically illustrates the reaction which may occur when the compound R SnCl is added be fore the polymer is recovered from the reaction mixture, e.g., at the beginning of the reaction. Equation 4 schematically illustrates the reaction which may occur when the compound .R SnCl is added after the polymer is formed. In reaction 3, x=n+l. These equations schematically illustrate that the three materials may react to form the disclosed compound which includes a chain containing tin and sulfur groups and which may be terminated by a residue from the R SnCl compound.

The novel product of this reaction may be characterized by the above noted formula which typically may have an analysis depending on the nature of R. When R is butyl (the product having been prepared, e.g., from R SnCl wherein R is butyl, a is 2, b is 1) the typical product may have an analysis 34%36-%, say 35% Sn, 9%-9.5%, say 9.2% S, and 0.5%-3%, say 2.5% CI. The linear product so formed may be readily soluble in toluene, in xylene, in benzene, in butylbenzene, in methyl butyl benzene, etc. Normally it may exist in the form of a free-flowing white crystalline powder, etc.

In accordance with a specific illustrative example of this invention which shows an illustrative technique for preparing a preferred embodiment of the novel composition of this invention, 42 parts by weight (0.4 mole) of fiamercaptopropionic acid, 100 parts by weight (0.4 mole) of dibutyltin oxide, 12 parts by weight (0.04 mole) of dibu-tyltin dichloride, and 800 parts by weight of benzene may be added to a reaction vessel fitted with stirrer, heating mantle, and Dean-Stark trap. This reaction mixture may be heated to reflux. During the reflux, 7.2 parts by weight (0.4 mole) of water may be recovered and separated which represents substantially 100% by weight of the theoretical recovery. The system may be adjusted to permit removal of the benzene and 800 parts may be recovered by distillation first at atmospheric pressure and then under vacuum of a water aspirator. The product may be recovered in substantially yield as a white crystalline powder.

In accordance with certain aspects of this invention, novel resin compositions particularly characterized by their superior heat and light stability may be prepared by mixing together a halogen-containing, preferably a chlorine-containing resin or organic polymer, and a stabilizing amount of a compound wherein R, R, and R" may each be selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, and alkaryl, a may be less than 3, and a+b may equal 3, and it may be 1-5, this compound having been prepared by the reaction of RR"Sn0,

HSCH CH COOH The polymers which may be stabilized by practice of this invention may be halogen-containing organic polymers typically those which contain chlorine atoms bonded to the polymer chain. These polymers may be homopolymers including polyvinyl chloride-type polymers, e.g. polyvinyl chloride, polyvinylidene chloride, etc. They may also include copolymers formed by the copolymerization of vinyl chloride or vinylidene chloride with other ethylenically unsaturated monomers. Ethylenically unsaturated monomers may be compounds which contain polymerizable carbon-to-carbon double bonds and may include acrylate such as acrylic acid, ethyl acrylate, acrylonitrile, etc; vinyl monomers such as styrene, vinyl acetate, etc; maleates such as maleic acid, maleic anhydride, maleate esters, etc. For convenience, reference will be hereinafter made to vinyl chloride polymers.

The vinyl chloride polymers may also contain plasticizrers such as dioctyl phthalate; lubricating agents such as stearic acid; pigments; fillers; etc.

Stabilizing amounts of the novel compositions of this invention may be 0.25 to 10, preferably 1 to 3, say 2 parts by weight of composition per 100 parts by weight of polymer, e.g. vinyl chloride polymer. Thus the preferred heat and light stable vinyl chloride polymer compositions of this invention may comprise 100 parts by weight of a vinyl chloride polymer and a stabilizing amount, typically 1 to 3 parts, of the compound of Formula 5 supra.

The novel heat and light stable compositions of this invention may be formulated by such techniques as milling, dry blending, Banbury blending, or any other commonly employed formulating techniques.

In order to point up the novel features of this invention and to illustrate the unexpected and superior results obtained by the practice thereof, the following illustr-ative comparative examples were run.

In a control (I) reaction, 543 parts by weight (2.22 moles) of dibutyltin oxide, 234 parts by weight (2.21 moles) of ,B-mercaptopropionic acid, and 300 parts by weight of acetone may be mixed together and refluxed at 59 C. for 55 minutes. The reaction mixture may then be cooled and filtered, the filtrate being saved for recovery of acetone. The filter cake may he vacuum dried to yield a crystalline white product in substantially stoichiometric (100%) yield. The product may typically have an analysis of 34.8% Sn and 9.4% S, and may have a melting point of 111 C. C. This material may be used as standard.

In a second (II) reaction conducted in accordance with this invention, 5 parts by weight of dibutyltin dichloride may be mixed with 100 parts by weight of the above noted control product (I) and reaction may be effected by grinding the reactants together and heating slightly.

In a third (III) reaction conducted in accordance with this invention, parts by weight of dibutyltin dichloride may be mixed with 100 parts by weight of the control product (I) and reaction effected by grinding the reactants together and heating slightly.

Each of these three comparative compositions may be blended with separate aliquots of vinyl chloride polymer having a specific gravity of 1.40, a Shore durometer D hardness of 80, and an ultimate tensile strength of 7000 p.s.i.g., sold under the trademark Geon l03-EP. In each case, 100 parts of vinyl chloride polymer may be blended with 2 parts of the composition.

These compositions may be thoroughly blended by placing the polyvinyl chloride on a two-roller differential mill which was oil-heated to a temperature of 163 C.l77 C. together with the hereinafter noted quantity of stabilizer and the mixture milled for about 5 minutes. A continuous band of the composition formed around one of the rollers. This band was cut and the composition was removed from the hot roller as a continuous sheet. Squares of this material measuring 2.54 cm. x 2.54 cm. were cut for heat stability testing.

Samples for light stability testing were prepared by press-polishing cm. x 15 cm. squares cut from the milled sheet. Press-polishing may be carried out by compressing the squares between chrome-surfaced plates at 177 C. and 25-30,000 p.s.i. for 3 minutes. Samples of each of the compositions were tested for light stability in an Atlas fadeometer by exposure therein for a total of 1300 hours. These samples were inspected at various intervals and were rated visually as to color change and degradation according to the following scale:

7no change 6slightest discernible change 5slight change 4moderate change 3burn line 2severe spotting or overall discoloration The results of the light stability tests are presented in Table I.

TABLE ILIGHI STABILITY It will be apparent from Table I that the vinyl chloride resin stabilized with the standard became quickly discolored after only 140 hours of test and that after 300 hours the rating had dropped to 4. In contrast, the first experimental sample (II) gave an initial discoloration after 220 hours and was satisfactory to about 520 hours, this representing an improvement by a factor of almost two; the second experimental sample (III) gave an initial discoloration after 400 hours and even after 700 hours the resin was still not undesirably discolored, this representing an unexpected improvement by a factor. of two-to-three.

The heat stability of the novel product of this invention was tested by placing 2.54 cm. squares in an oven regulated to maintain a temperature of 190 C. Sainples of each composition were removed from the oven 7-clear, Water-white 6off-white I 5slightest degree of yellowing 4definite yellow color 3deep yellow-brown color 2deep brown color 1-dark brown to black color The length of time in minutes required to reach a value of 3 or less may be recorded as the Heat Stability Value.

The heat stability value of each of the three compositions tested was found to be 60 minutes, which is satisfactory.

It is completely unexpected that the above-tested specimens embodying the novel stabilizers of this invention possess such superior ability to effect stabilization against deterioration by light while simultaneously retaining the ability to effect stabilization against deterioration by heat.

Other examples of stabilized vinyl chloride polymer resin compositions which may fall within the scope of this invention and possess unexpectedly superior properties with respect to heat and light stability will be obvious to those skilled in the art. Although this invention has been illustrated by reference to specific examples, changes therein which clearly fall Within the scope of the invention Will be apparent to those skilled in the art. It is therefore to be limited solely by the scope of the appended claims.

I claim:

1. The method of preparing a novel composition which comprises reacting R SnCl with substantially equimolar amounts of RRSnO and HSCH CH COOH, wherein R, R, and R are each selected from the group consisting of alkyl, alkenyl, alkynyl, cycloalkyl, aryl aralkyl, and alkaryl, a is less than 3, and a+b equals 3.

2. The method of preparing a novel composition as claimed in claim 1 wherein R SnCl is reacted in amount of 0.050.20 moles per mole of HSCH CH COOH, and said RRSnO and HSCH CH COOH are present in substantially equimolar amounts.

3. The method of preparing a novel composition as claimed in claim 1 wherein R, R, and R" are lower alkyl.

4. The method of preparing a novel composition as claimed in claim 1 wherein R, R and R are the same.

5. The method of preparing a novel composition as claimed in claim 1 wherein R, R and R are butyl, a is 2, and b is 1.

6. The method of preparing a novel composition as claimed in claim 1 wherein R SnCl is dibutyltin dichloride.

aralkyl, and alkaryl, a is less than 3, a+b equals 3 and n equals l-S.

8. A novel composition wherein R, R, and R are lower alkyl, a+b equals 3, and n equals 1-5.

9. A novel composition wherein R, R, and R" are the same and are each sewherein R, R, and R" are butyl, a is 2, b is 1, and n equals 1-5.

References Cited by the Examiner UNITED STATES PATENTS Mack et a1. 26045.75 Leistner et al. 260-45.75

Mack 260429.7 Cramer et a1. 260429.7 Polster 260429.7

TOBIAS E. LEVOW, Primary Examiner. LEON J. BERCOVITZ, Examiner.

G. W. RAUCHFUSS, JR., W. F. W. BELLAMY,

Assistant Examiners. 

1. THE METHOD OF PREPARING A NOVEL COMPOSITION WHICH COMPRISES REACTING RASNCLB+1 WITH SUBSTANTIALLY EQUIMOLAR AMOUNTS OF R''R''''SNO AND HSCH2CH2COOH, WHEREIN R,R'', AND R'''' ARE EACH SELECTED FROM THE GROUP CONSISTING OF ALKYL, ALKENYL, ALKYNYL, CYCLOALKYL, ARALKYL, AND ALKARYL, A IS LESS THAN 3, AND A+B EQUALS
 3. 7. A NOVEL COMPOSITION WHEREIN R, R'', AND R'''' ARE EACH SELECTED FROM THE GROUP CONSISTING OF ALKYL, ALKENYL, ALKYNYL, CYCLOALKYL, ARYL, ARALKYL, AND ALKARYL, A IS LESS THAN 3, A+B EQUALS 3 AND N EQUALS 1-5. 